The reverse searing method is more forgiving in terms of timing, but not any better if you can get the timing right. As a side note, I can't begin to count or describe the altered states of consciousness in which I've managed to cook steaks perfectly well... er... perfectly mid rare.
When you use oil, butter or any other sort of fat in aid of searing, you use very, very little. Less than you'd use for a saute. You can sear in olive oil, no big deal; but I think durangojo is right -- good olive oil is wasted. Butter is doable, but very difficult because it burns at such a low heat.
If you're doing a pan sauce with mushrooms, the suggestion to roast the mushrooms in a dry-ish pans before building the sauce is good. You can use the same pan you used to pan roast the meat to pan roast the mushrooms. More about the mushroom pan sauce later.
Preheat your oven to 375F. You'd use a hotter oven in a pro kitchen, and Phatch would have you use a slower one. The reason I like 375F for home cooks is because it's an easy temperature to time; figuring 12 minutes a pound to medium rare. More about timing later.
You want to temp (allow them to come to near room temperature on the counter) your steaks before searing. I like to do it in a splash of Worcestershire and red wine. After the meat is temped, pour off any marinade and rub it with your favorite rub. If you don't have one, you can try my "Basic Beef Rub." I recently posted an espresso/cocoa variation here in CT you might like for this purpose.
Note that you want to avoid salting the meat -- which includes using a rub with salt -- until just before you cook it.
Preheat a heavy pan, large enough to hold your steaks without crowding, over a medium-high flame. When the pan is hot enough to saute, pour a very little oil in the pan. If the oil smokes, it's ready to go. If it flows very freely, and has a little bit of shimmer floating over the simmer, it's also ready. If it flows slowly and doesn't cover the pan surface completely, leaving little gaps and holes, it's not ready.
If it's not ready, continue heating until the oil flows very freely. You only need enough to barely cover the bottom of the pan, and when it's hot you can pour off any excess.
Add the steak(s) to the pan. Now, leave them the heck alone. Don't touch them. After two minutes shake the pan gently. If the steak slides freely (i.e., "releases") it's ready to turn. If not, it isn't. Give it another 30 seconds and check again. Then, another thirty seconds. If, after 3 minutes it doesn't release, knock it sideways with your tongs or spat, and turn.
For what it's worth, the "release point" tells you that the meat is perfectly seared. More or less is less, if you catch my drift.
Sear the other side for 1 minute only, and put the steak in the oven. The residual heat from the pan will continue to sear the bottom. If you put it in the oven with a perfect sear, it will overcook and become hard during the roasting period. But if the bottom's a little undercooked, so what? Your steak only has one presentation side.
Estimate how long you had the steak searing in the pan, and subtract that time from the 12 minute per pound total. That's how long the steak needs to stay in the oven to hit mid-rare. You can touch test if it you like (and you should, you always should) with two minutes left to go, then every two minutes thereafter. For example, let's say you had one thick porterhouse, large enough for several people -- around 2-1/2 pounds. The 12 min per pound rule nets 30 minutes total. Subtract four minutes for the sear (if that's how long it took), and you get 26 minutes. Start touch temping at 24 minutes. If it's only a 1-1/4 pound steak, 15 - 4 = 11, so start testing at 9.
Make sure to touch temp both sides.
If you don't know how to touch temp accurately, use an instant read meat thermometer and touch. You'll calibrate your sense of touch a lot quicker than any of the comparison tricks (nose; ear, lip, nose; thumb muscle; etc.). I'd rather see you use a thermometer than dance around grabbing your crotch and nose. Remember touch temping is limited to relatively thin cuts of meat, you can't accurately touch temp a large roast.
When the meat has an internal of 120 - 125 it's done. Remove it to a separate plate to rest. Depending on how thick they are, steaks should usually be rested for 7 - 12 minutes.
Return the pan to the flame and deglaze it with a splash brandy or madeira (if you can't get reasonably price madeira, an "off-dry" sherry like an Amontillado or dry Marsala are good substitutes). I prefer brandy for this. Scrape the fond off, and cook over medium-high until the liquid boils off.
Add enough fat to the pan to saute. You can use butter with a little oil (keeps the butter from burning), olive oil or a neutral oil. It's up to you and your taste. Add your aromatics. I prefer straight, shallots, chopped very fine; but you may like onions, garlic, or some combination. When the aromatics are fragrant, add your cleaned and dry sliced mushrooms. Try and spread them in the pan evenly, in order to get some browning. You only have one chance to brown mushrooms, because when you start stirring them they'll start releasing water, which will interfere with the browning reaction.
After about two minutes, turn the mushrooms. If you can flip-turn, so much the better; but if you have to use your spat it's OK. Now you may salt and pepper the mushrooms lightly.
If you like, you can add about a tbs of tomato paste now, to help stiffen the eventual sauce as well as for taste. If you do, move everything around in the pan so the paste cooks a little before you add the rest of the liquid.
Add a 50/50 mix of beef stock and Madeira, and a splash of Worcestershire, and cook the sauce down until it reaches the desired consistency. For most people that's going to be a bit more than a 50% reduction; so measure the stock/wine mix into the pan accordingly. When the sauce begins to show enough structure, add some chopped parsley, some fresh thyme, and other fresh herbs -- marjoram or tarragon for instance -- if you like. Reserve some of the parsley. Taste for salt, and adjust.
Plate the steak, pour the mushroom sauce over, and sprinkle with freshly chopped parsley and a few pieces of chive. You can also use a bit of lemon zest to brighten the flavors up, but I like my mushroom pan sauce on the mellow side.
It may seem like a lot, but that's only because it's so exhaustively broken down. This is actually a fairly easy way of cooking steak at a high level.
Edited by boar_d_laze - 11/29/11 at 7:33pm